Carburation device



Sept. 19, 1933.

H. w. HESS CARBURATION DEVICE Filed Aug. 12, 1929 Patented Sept. 19,1933 CARBURATION DEVICE Harry W. Hess, Milwaukee, Wis, assignor toCarburetor Control Company, a corporation of Nevada Application August12, 1929. Serial No. 385,269

8 Claims.

This invention relates in general to the carburation or vaporization andconditioning of fuel for combustion thereof for energy producingpurposes, and the invention finds particularly useful application inconnection with the admission of a supply of properly mixed liquid fueland air to the cylinders or manifold of an internal combustion engine,although the utility of features of the invention is of more generalscope and application; but, for purposes of presenting the invention,the disclosure will be more particularly directed to the application ofthe invention for use with an internal combustion engine of the'liquidfuel type, such as is ordi narily used on automobiles.

Control of an internal combustion engine is secured through regulationof the supply of hydro-carbon fuel and air which produce the fuelmixture fed to the cylinders. Inefiiciency of operation and reducedpower in the operation of an internal combustion engine are incidents ofoverrich or over-lean mixtures of fuel and air supplied to the enginecylinders; and the supply of an over-rich mixture has the further defectof causing excessive carbon deposits in the engine cylinders duringoperation. In order to insure efiicient operation and desired uniformityof power response and regularity of acceleration,

it is ordinarily desirable that, for the various po sitions of thethrottle, or valve device regulating the admission of fuel mixture tothe engine, the proportions of fuel and air should be constantthroughout the entire range of engine speed, or from idling condition tofull-open throttle condition.

A general object and purpose of the present invention is the provisionof an improved form of carbureting device capable of readily insurringuniformity to the desired degree in the-matter of the proportions of airand vaporized hydro-carbon fuel in the combustible mixture, throughoutthe full range of control, to the end of attaining smooth operationthroughout the entire speed range, with fast acceleration and highmaximum power, along with a high degree of general efficiency andeconomy in the operation of an internal combustion engine with which thecarburetor is associated.

The present invention contemplates as a particularly desirable featurethereof the provision of a carburetor for preparing and feeding to aninternal combustion engine or the like a mixture of air and vaporizedfuel, wherein the supply of fuel is definitely regulated with respect tothe particular operating speed or power desired, as may be determined bythe position of a throttle, and is coupled with the supply in anautomatically controlled manner of just the desired amount of air toproduce with the fuel supplied a fuel mixture composed of desirablyuniform proportions of air and fuel, to thus insure efiicient operationof the engine. And, in accordance withcertain features of the invention,the control of the supply of liquid fuel is secured through utilizationof an improved form of fuel-- controlling valve affording fineregulation and metering of the fuel and rendering the degree of openingof such valve definitely proportional to the degree of opening of thethrottle. And a further feature of the invention includes theutilization of an air admission controlling valve whose operation isautomatically responsive to the suction drag or degree of depressionpresent in the engine cylinders, or manifold associated therewith, asdetermined by the position of the throttle, the design and arrangementof parts of this air controlling valve being such as to insure a'readilycontrolled automatic operation of the valve with an immediate anddelicate response, from its minimum-open to its maximumopen position,with consequent maximum available power and maximum economy in thematter of fuel consumption.

Various additional features and objects of this invention, concernedwith the controlled supply of airv and fuel to the carburetor and of thecombined or mixed air and fuel to the engine, and structuralarrangements and mechanical details concerned th rewith, will beapparent from the more detailed description of the invention containedin the specification hereinafter and from the accompanying drawingdisclosing embodiments of the invention, and will be more particularlypointed out in the claims.

In the drawing:

Fig. 1 is a broken sectional elevation of a carburetor embodyingfeatures of the present invention, the plane of the section being thatof the line II of Fig. 2.

Fig. 2 is a view similar to Fig. l, the plane of section being that ofthe line IIII of Fig. 1.

Fig. 3 is a broken sectional elevation of the device as shown in Fig. 2,the section being in the plane of the line III-III of Fig. 1.

Fig. 4 is a bottom plan view of the device shown in Fig. 2.

Fig. 5 is a View similar to Fig. 3, with parts broken away, andembodying modifications of certain features.

In accordance with the disclosure of the draw- 19110 ing, 5 indicates afuel float chamber such as is customarily associated with carburetorsfor use with internal combustion engines of automobiles; and 6 indicatesthe body portion, of rectangular cross-section, of a riser element orchamber into which the fuel and gas are admitted and wherein they aremixed prior to the supply of the mixture to the engine cylinders. Thefloat chamber and riser chamber are preferably, as indicated, formedseparately but are so designed as to be readily assembled as a unit anddetachable from one another when necessary. The float chamber isprovided with an enlarged hollow extension '7 at one side thereofforming a portion of or having its interior communicating with the mainfuel chamber 5, and this extension 7 is provided with spaced projections8 and 9 extending at substantially right angles from a portion or pad 10formed on a side wall of the extension 7.

The projection or extension 8 is provided with a bore 11 communicating,as will be described hereinafter, with the interior of theextension 7 ofthe float chamber; and there is provided at the upper side of theextension 8 at a medial point thereof, an aperture communicating withthe bore 11 and in which is mounted, preferably in a detachable manner,a fuel supply nipple 12 having a nozzle portion 13 of suitable knowndesign at its upper end and projecting axially into a central aperture1% through the bar-like upper projection 9. The diameter of the nipplesuch that it can be inserted to and from operative p sition through theaperture. 14, and the nozzle portion 13 is sufficiently reduced as toleave annular space of ample size between the outer wall of the nippleand thewall of the aperture 14 to permit the passage therethrough of asupply of air to satisfactorily take care of idling conditions of theengine, the walls of the aperture 14 projecting to a substantial extentabove the nipple, thus confining the air passing through the aperture 14in such a manner as to insure its ready contact and commingling with thefuel drawn through the nozzle 13, during operation of the assembledcarburetor.

The bar-like projections 8 and 9 preferably project from the extension 7of the float chamber to such a point that when the wall of the riserchamber 6 is held against the face of the pad 10, with these projections8 and 9 extending through an aperture formed in such side wall, theouter end of each of the projections 8 and 9 is in close proximity to orabuts against the inner face of the opposite wall of the riser chamber.The float chamber 5 and the riser chamber 6 are shown assembled inoperative position, with the axis of the aperture 14 and the fuel nozzle13 in alineinent with the axis of the riser chamber, and with theprojections 3 and 9 extending through an aperture, with a relativelyclose fit therein, in the corresponding side wall of the riser chamber,adjacent parts of this side wall abutting fiatwise against the face ofthe pad 10 on the extension '7 of the float chamber. A raised portionmay be formed on the outer face of the pad 10 to enter and fill thatportion of the aperture in the adjacent side wall of the riser chamberunoccupied by the projections 3 and 9. Extensions or lugs 16 arepreferably formed at the side edges of the pad 10 and embrace the sidetvalls of the riser chamber to hold the latter opposite side wall of theriser chamber, and through the latter side wall, these screws 1'? beingthreaded into apertures in the adjacent ends of the spaced projections 8and 9. The clamping plate 18 may be provided at its side edges withprojections or lugs 19 which engage the faces of the adjacent sidewalls'of the riser chamber and assist in holding the parts againstlateral displacement. With the clamping screws 17 drawn up to position,the riser chamber is securely clamped in operative position relative tothe float chamber 5 and its appurtenant fuelfeeding parts in such amanner as to insure the passage of fuel from the float chamber and toand through the fuel discharge nozzle 13.

Fuel is fed from the float chamber 5, a regulating valve 20 controllingthe passage of fuel from the hollow extension 7 of the float chamber.This regulating valve comprises a fixed seating element 21 of tubularformation having a slightly flared or conical seating face on itsinterior, with the larger diameter of the flared seat atthe upper endthereof, where it opens to the fuel in the extension chamber 7, andtapering, in diameter, preferably with a straight taper, toward itslower end. A movable valve element 23 of the needle type, and preferablystraight sided or cylindrical throughout its'active controlling portion,is arranged to be reciprocated within and to cooperate with the taperedseating face or bore of the seating element 21, to meter or control thepassage of fuel through the valve. As indicated, the seating element 21-is preferably made up in the form of a bushing threaded adjacent itsupper end into an aperture formed in the lower wall of the extension 7of the float chamber. e

The quantity of fuel that may pass through the valve is determined bythedegree to which the needle is displaced upwardly from its 10W6Y- mostposition wherein the lower end of the needle is in engagement, orsubstantial engagement, along an annular surface or a line, with theadjacent portion of the interior seat 21. By shifting the position ofthe needle 23 upwards or downwards within its flared seat 21, an annularopening of variable size is formed between the lower end of the needleand the portion of the flared seat adjacent thereto, a feature whichper-- mits extremely fine metering or regulation of the amount of fueldischarged downwardly through the valve. Through the presence of agradual contraction up to the metering throat between the end of theneedle 23 and its seat 21, the same being located at a relatively lowpoint in the assembly where it is subjected to considerable head, fuelis discharged through the contracted annular metering passage with.sufficiently velocity to keep even a fine opening clear. Fuel dischargesfrom'the valve 20 into a chamber or supply well 24, preferably formed bya detach able cap or thimbIe-Z H threaded into the wall of a bore orapertured portion at the lower side wall of, the extension '7 of thefloat chamber. Communication is established between the sup-- ply well24 and the bore or passage 11 in the prcjection 8 communicating with thenozzle 13, through a passage or bore 25 formed through the lower wall ofthe extension 7 of the float chamber.

Air enters the carburetor through the lower end of the riser chamber 60frectangular crosssection, this lower end of the latter, in the formshown herein, being cut away at an angle of approximately 15 degrees soas to facilitate the enxvi trance of the air from a lateral direction.The supply of air through the lower portion of the riser chamber andinto the upper portion thereof or mixing chamber, indicated 35, iscontrolled by means of a special type oi valve which is automaticallyresponsive in its operation to the adjustment or? the throttle controlthe suc tion drag or depression of the engine cylinders incidentthereto. This air controlling valve is shown in the form of a pair ofopposed, similarly shaped and symmetrically arranged resilient leaves28, having their lower secured in position adjacent opposite Walls, hypivotally mounting these lower ends on pins so as to permit oscillationthereon, as indicated at 39. These ient leaves are of under normal orunbiased cont ons, and are so dimensioned and disposed in the riserchamber that theiintermediate portions are to hear lightly st the sideWalls of projection or cross bar 9 which surronids the discharge end ofthe 13, as indicated in full lines in Fig. 3. The upper ends of theseresilient leaves 29 bear against the inner fa es of the adjacent sideWalls of the mixing chamber 56, being slightly rounded at these ends, asindicated at 32, to facilitate sliding movement of the ends along thewall of the chamber. Pins 34 through opposed side Walls of the chamberand serve to retain the upper ends of the springs against appreciahledisplacement away from the side walls with Whi they engage, While stillpermitting their. displacement longitudinally along these side Walls asthe interined .e portions of the leaves flatten out during. operation ofthe carburetor.

It is desirable that the intermediate portion of the resilient leaves28, 29 Where they approach one another most closely be adjacent,preferably slightly above, the discharge end of the nozzle for the airpassing through this throat or contracted per at 31, or the venturiformed by the leaves and the side Walls is at maximum velocity andexerts a benericial d ag on the fuel supplied through the nozzle andimparts a desirable breaking-up erlect on the particles of fueldischarged frorn'the nozzle.

The portions of the resilient leaves 28, 29 below the cross par 9,corresponding to the point of greatest contraction slot the passagebetween the inwardly bulged portions of the opposed resilient leaves,are or full Width, i. they extend across the lull width of the passagethrough the riser chamber their edges cooperate with opposed straightsided walls of this chamber, preferably with a minimum clearance, so asto permit the desired movement of the spring transversely thereof Whileat the same time preventing leakage of pressure air to the rear side ofthe leaves.

portions of the resilient leaves 28, 29above elite on cross bar 9 arerecessed or cut away to mit the rear sides of these leaves throughouttheir full length to be exposed to any depression or vacuu-.. existingin the mixing chamber, due to the suction drag of the engine cylinders.To secure this effect each of the re-' silient leaves 28, 29 may he cutaway, as indicated, at its side edges, a point appreciably vs the iwar ybulged intermediate part of the spring which is biased against the crossbar 9. Further, t... ougn this gradual red .ction of the width of theleaves at their upper ends, these portions the leaves have decreasedinertia and are more .rlexi lo, and. hence more read ily displaceable ordistortable from normal hiase condition during operation of thecarburetor.

having the upper ends of the resilient leaves 28,

29 hearing against the walls of the chamber, ency to uncontrolledvibration of t as leaves pulsation during operation is min ed.

Through the arrangement of the arts of the valve, all of air admitted tothe in her is metered or controlled, by reason of its passage throughthe throat 3' of Venturi tube of automatically va formed between theinwardly .ilged or contracted portions of the s its 23, 29, the e r ofthe lower portions or l or with the opposed Walls of the chamber s thatthere is no appreciable or. air heen the edges of the leaves and theside Walls of the charnloer'at the inlet of the contracted throat, suchmight cause undesirable variations the proportion of air and fueladmitted to the mi ing chamber. With this arrangement, the lowerportions of the resil suction a variahle degree toward flattened condiion, dc Li pending upon the speed of operation engine, a material factorin avoiding sluggish ness in the opening and closing movements of theair controlling valve and in insuring the de sired ready and delicateresponsiveness of this air valve in automatically providing the requiredhow of air to the mixing chamber and t e uniformity of proportions ofand Fuel drawn in vapor form into t. mixing chamber from the nozzle 13is surrounded by and quite thoroughly mixed with through the opening 14in the cross bar 9 and between the Walls of Venturi throat "1e sizeformed between the inw dly bul c. mediate portionsof the res-ill ntleaves 2 I which, as they are distorted more or less from their normalbiased positions during oi the engine, have the effect of varying thecrosssectional area of this mixing chamber at its lower portion.

The mixture oi air and vaporized iuel is fed from the mixing chamber 3'5the engine cylindel's, or the manifold. associated therewith, through acontrolling throttle valve ll of butterfly type, indicated outline forcooperation. v; passage of rectangular cross-s upper portion of thechard: r tle valve mounted on a through the side Walls of the eralolymounted in der; enlarged cap portion of the riser. The t 'llOL maythrough spindle 42 and an actua. nected to a crank arm 45 fl: thespindle, by a handle or any position convenient to 0 here shown in theform of a in a projection i"! on th ci r With a fixed stop or projectionto variably determinative closed, position or" the re desired idlingconditions of cap portion 43 is preferably separate casting,particularly Where chamber can be formed of stock shapes and sizes andthe machine work necessary to constitute a suitable mounting for thethrottle valve and parts, may be done on the part 43 before the latteris attached to the riser.

While certain features of the present invention may be realized with acarburetor wherein there is a single fixed or manually controllableopening for supply of fuel to the carburetor, some variation intheamount of fuel supplied being aiforded by differences in suction dragexerted by the engine due to variations in speed of the latter,nevertheless, the most desirable operating characteristics attained in acarburetor of the general type described above wherein the supply offuel to the carburetor is to correspond more definitely and assuredly tothe requirements of the engine in the n atter of speed and power.Accordingly, the niov ile needle element 23 of the fuel. regulatingvalve is caused to be actuated to a position to produce an openingthrough the valve 28 which always bears a desired definite relation tothe position of the throttle valve, and hence, to the required speed andpower of the engine.

As indicated, the needle valve 23 is fixedly attached to a rod 51, as byhaving the upper end of the needle valve fitting within a socket at thelower end of the rod 51 and having flexible side walls which, after theneedle is inserted into position in the socket, be clamped and held inposition about the needle by means of a clamping nut 52 threaded uponthe flexible side walls of the socketed portion of the rod. This rod 51preferably passes out of the chamber formed in the extension 7 of thefloat chamber, through an apertured cap or bushing 53 secured, as bythreading, in an opening formed in the upper wall of the extension 7 ofthe float chamber. This opening in which the bushing 53 is detachablysecured, is of suiiicient size to permit the ready removal andreplacement therethrough of the tubular seating element 21 of the fueregulating valve 20 which is formed at its upper end for engagement witha suitable tool. A compression spring 5 1 surrounds the rod 51, bearingat its upper end against the under side of the cap portion of thebushing 53, and at its lower end against the clamping nut at the lowerend of the rod 51; and this spring serves to bias the needle valvedownwardly toward closed or desired idling position, insuring automaticreturn to lower position whenever the needl is relieved of operatingpressure.

As indicated, the throttle valve 41 is connected to the operating rod 51of the needle 23 of the fuel metering valve, for one-way positiveoperation of the latter, through a link 55 flexibly connected to theupper end of the rod 51 and to a crank 56 loose upon the spindle 42 ofthe throttle and provided with an off-set lug or extension 58; and anadjustable stop 59 threaded through a projection so on a crank arm 61fixed to the spindle e2 bears against the upper side of the projection58. With this arrangement, operation of the throttle ll toward full-openposition, that is, in a clockwise direction, as viewed in Fig. 2, causesthe opening of the needle 23, through the action of the stop 59 bearingupon the projection 58 on the loose crank 55 to which the connectinglink 55 is attached. ihis operating connection is such that as thethrottle opened, the needle valve is opened to a corresponding desiredamount, definitely determined by the lever arm of the crank 55 and thedegree of taper of the valve seat 21; and then, as the throttle isreleased or closed, the needle 23 of the fuel metering valve isimmediately forced, through the ac-v tion of the biasing spring 54, to aclosed or partly closed position, corresponding to the new position ofthe throttle, at which time the projection 58 on the loose crank 56abuts against the adjustable stop 59 associated with the operating partsof the throttle.

The initial or idle position of the fuel metering valve, and the amountof fuel supplied for a particular throttle opening may be adjusted atwill by adjusting the position of the stop 59 against which theprojecting lu 58 on the crank 56 abuts, this adjustment, coupled withthe effect of the biasing spring 54, serving to raise or lower theneedle 23 relative to its seat 21 to thereby vary the opening throughthe valve. Further adjustment of the fuel metering valve may beaccomplished by replacing the needle 23 with another of differentdiameter which, for a given needle position, affords a correspondinglylarger or smaller passage between the lower end of the needle and theseat 21.

In order to provide for opening of the fuel metering valve 20independently of the throttle and its adjustment relative to the fuelvalve, such as may be necessary for cold-weather starting, a crank 63 ismounted loosely on the spindle i2 of the throttle and is provided with aprojecting nose 63" which, on suitable actuation of this crankin aclockwise direction, as by means of a connecting rod passing to theoperators position, engages with the outer end of the extension 58 onthe crank 55, shiftingthe latter in a clockwise direction and therebylifting the needle 23 of the fuel valve away from its tubular seat tothe desired degree. On relieving the crank 53 of operating pressure, thebiasing spring 54 immediately shifts the needle valve to a closed orother position, corresponding to the position of the throttle at thetime.

An auxiliary supply or bypass for the feeding of fuel from the floatchamber 5 to the fuel nozzle 13 maybe provided through a port 6% in thelower side wall of the hollow extension 7, this port com municating withthe well 2 A needle valve 65 cooperates with this port for varying thesize thereof or closing the port, a portion of this valve passingthrough the upper wall of the hollow chamber '7 and formed at its upperend to permit adjustment from the outside of the casing of the degree ofopening of the valve. Or, this valve 65 may have its upper end formedfor connection to a loose crank such as 53 for adjustment thereby,through an operating connection, from the operators position.

Assume that the engine has been started and is operating under idlingconditions, the throttle being opened or cracked slightly, as determinedby the adjustment of the stop screw 45, and with the fuel metering valveopen to its predetermined or nearly closed position, and the air valvewith the inwardly bulged intermediate portions against the sides of thecross bar 9, as

ure is drawn therefrom throughfuel is fed under these conditions, justenough to maintain the engine in operation with no load thereon.

In order to bring the engine up to any desired operating speed, thethrottle is actuated to a position corresponding to the desired speed,and the fuel metering valve, through the operating connectiontherebetween and the throttle during its opening adjustment, isalsoopened to a degree corresponding to the particular settingof thethrottle. The suction of the engine cylinders is immediately effectiveto draw an increased amount of fuel through the supply nozzle 13 and,likewise, the increased suction due to the opening of the throttle, isimmediately efit'ective to cause an increased supply of air through theair valve, the leaves 28, 2 of the air valve moving outwardly towardtheir flattened position, due to the differential pressure exertedthereon by the incoming air passing through the throttle of the venturiformed by the intermediate bulged portions of the resilient leaves.These leaves are distorted or flattened to a position determined by thedesign of the leaves and the particular setting" of the throttle, theresult being that the opening between these leaves is just sufficient tosupply under the suction drag conditions incident to the particulardegree of opening of the throttle, just the required amount of air formixture with the supply of fuel passing through the fuel metering Valvewhose position is likewise determined by the position of the throttle.

In the modification shown in Fi 5, the riser chamber 6 is indicated asbeing of special shape particularly designed to provide space forreceiv-- ing the opposed leaves 28, 29 constituting the air valve whenthe latter is in maximum open position, to the end that, when this valveis in maximum open position, there will be a through passage between theopposed leaves which is substantially equal in cross-sectional area tothe.

inlet portion of the riser chamber. As indicated, opposed side walls ofthe riser chamber are distorted outwardly adjacent the leaves, from'thepivotal point to the upper end th reof, thus providing recesses whichreceive the springin its maximum open position, indicated in dottedlines.

While the inherent resilience'of the leaves 28 and 29 themselves,constituting the automatic air valve, is relied on wholly in theparticular embodiments of the invention described herein,

to insure the properopening of the air valve at" times, certaindesirable results are attainable 'th valve leaves in connection withwhich separate springs are utilized in whole or in part to bias andreturn the leaves to minimum open position.

"it is an interesting feature of the operation .of the presentcarburetor that the response in the matter of an increased or decreasedsupply of air, corresponding to any opening or closing adjustment of thethrottle is immediate, for the operation of the throttle varies topressure to .which the rear sides of the resilient leaves are exposed,thus distorting or destroying the normal equilibrium or balance existingfor the theretofore existing throttle adjustment. Through the abovedescribed several, features of design, the highly desirable result isattained that a uniform proportion of air and fuel is supplied to theengine from the minimum opening or idling position of the throttle andassociated parts to the maximum opening thereof, corresponding tomaximum speed of operation of the engine. And further, through thisdesign and arrangemerit of parts, the depression or suction available inthe mixing chamber or at the discharge side of the air: valvevaries at auniform rate from idling or minimum open position of the throttle,corresponding to minimum operating speed, to maximum opening, or maximumspeed condition of the engine, the general result being that maximumpower and maximum economy of fuel is available under all operatingconditions the engine. 'While the riser chamber 6 is shown asbeing ofrectangular cross-section throughout, any piion of the sameabove theactivecontrolling portion of the leaves 28, 29 of the air valve may,with reasonably satisfactory results, be of a section other thanrectangular. However, with a butterfly valve of rectangular outlinecooperating with a correspondingly shaped casing, the open area orpassage through the latter more readily provides a passage of uniformlyvarying area as the throttle is opened. Likewise, the rectangular formof throttle cooperates better with a simple design of fuel meteringvalve of relatively straight taper, to secure the desired uniformity ofproportions of fuel and air, as the throttle is opened.

It should be understood that the invention claimed is not limited to thedetails of construction and operation described hereinabove, for obviousmodifications within the scope of the appended claims will occur tothose skilled in the art and are to be considered as included within thegeneral scope of the invention.

't isclaimed and desired to secure by Letters Patent:

l.v In a carburation device, the combination of a fuel mixing chamber,means for automatically controlling the admission of air to said mixingchamber, said means comprising a leaf valve having an intermediateportion resiliently urged toward a position to close the through passageof air and movable transversely across a portion of thecasing elementhaving opposed parallel sidewalls with which the edge portions of saidleaf valve cooperate to prevent the passage of air from the inlet sidethereof between said edges and said walls of the valve chamber, whileperinitting free exposure of the rear side of said leaf valve to thepressure conditions present in said mixing 1 chamber.

, 2. In a carburation device, the combination of a fuel mixing chamber,of an automatically operated valve for controlling the admission of airto said mixing chamber, said valve being resiliently biased to closedposition and being movable to open position in response to the suctionavailable in said mixing chamber, said valve including a plurality ofsymmetrically disposed and opposed leaves providing a Venturi throttleof variable throat opening, and a casing element therefor having opposedparallel side walls with which the edge portions of said leavescooperate in a substantially fluid tight manner during movement of saidleaves from their closed position wherein they approach each other to amaximum extent, whereby the inlet sides of each of said leaves is opento the pressure of incoming air whereas the rear side of said leaves isfreely exposed to the suction available in said mixing chamber.

3. In a carburation device, the combination of a casing having therein,a fuel supply chamber, a fuel mixing chamber, and means for controllingthe supply of fuel from said supply chamber to said mixing chamber, saidmeans comprising a nozzle disposed adjacent said mixing chamber, and afuel controlling valve controlling the passage of fuel from saidsupplychamber, said valve including a seat member of tubular formation havinga flared internal seat, mounted in the lower wall of said fuel supplychamber, a movable controlling needle disposed within said tubular seathaving its end portion of a cross-sectional area at least equal to thatof the shank portion of said needle, said end portion constituting theeffective valve element for varying the size of the effective passagetherethrough between said seat and the end'of said needle.

4. In a carburation device, the combination of a fuel supply chamber, afuel mixing chamber, and means for controlling the supply of fuel fromsaid supply chamber to said mixing chamber, said means comprising anozzle disposed adjacent said mixing chamber, and a fuel controllingvalve controlling the passage of fuel from said supply cham-' her, saidvalve including a seat member of tubular formation having a flaredinternal seat, a movable controlling needle disposed within said tubularinlet having its end portion of a cross-sectional area at least equal tothat of the shank portion of said needle, said end portion constitutingthe effective valve element for varying the size of the effectivepassage therethrough between said seat and the end of said needle, athrottle for controlling the fuel mixture discharged from said mixingchamber, and a mechanical connection between said throttle and said fuelsupply valve for insuring the opening of said fuel supply valve to adegree proportionate to the opening of said throttle.

5. In a carburetor, the combination of a fuel mixing chamber, means forcontrolling the admission of air to said mixing chamber, said lattermeans comprising a plurality of leaves uniformly distributed about theaxis of said mixing chamber and cooperative with wall portions at theinlet side of said mixing chamber to produce a Venturi throttle ofvariable throat opening, the rear faces of said leaves being exposed toonly the pressure in the mixing chamber at the discharge side of saidair valve, and a fuel supply nozzle having its discharge opening betweensaid leaves adjacent the point of greatest constriction therebetween.

6. In a carburetor, the combination of a fuel mixing chamber, anautomatically operable valve for controlling the admission of air tosaid mixing 'chamber, said valve comprising a plurality of leavessymmetrically disposed about the axis of said mixing chamber and forminga variable ven'- turi therein and yielding biased toward each other todecrease the size of the Venturi passage formed therebetween, saidleaves cooperating with the walls of said chamber to close the rearfaces of said leaves to pressure other than that existing in the mixingchamber beyond the throat of said venturi, an element extending acrosssaid chamber and serving as a stop to limit the movement of said valvemembers toward each other, said stop being apertured in substantialalinement with the axis of said mixing chamber, and a fuel dischargenozzle extending into the aperture in said stop and spaced from thewalls thereof, to insure an air passage about the discharge end of saidnozzle when said leaves are in position to provide minimum openingtherebetween.

'7. In a carburetor, the combination of a mixing chamber, a throttlevalve of rectangular outline cooperating with the walls of a passage ofrectangular cross-section for controlling the discharge from said mixingchamber, and a reciprocating valve for controlling the supply of fuel tosaid mixing chamber, said fuel valve being asso ciated with saidthrottle for actuation in synchronism therewith and being biased towardclosed position independently of said throttle, the operating connectionbetween said throttle and said fuel valve insuring the positiveactuation of said fuel valve to open position and the automatic returnof said fuel valve following closing movement of said throttle.

8. In a carburetor, a two-part casing structure, one part of said casingincluding a fuel supply chamber, a fuel discharge nozzle, and a valvefor controlling communication between said fuel supply chamber and saidfuel nozzle, and a second part of said casing including a mixingchamber, a throttle valve for controlling the discharge from said mixingchamber, and an air admission controlling valve comprising a pluralityof separable leaves biased toward each other for controlling theadmission of air to said mixing chamber, and means for securing the twoparts of said casing in operative position relative to each other, withsaid fuel discharge nozzle disposed in substantial alinement with theaxis of said mixing chamber and located at the point of minimum openingbetween

